We know that the arc of a circle is a part of the circumference of the circle.
The circular region enclosed by two radii and the corresponding arc of a circle is called the sector of a circle.
The angle subtended by the corresponding arc of the sector at the centre of the circle is called the angle of the sector.
Area of a Sector of angle

Area of a Sector of angle

Length of an arc of angle

Length of an arc of angle

The circular region enclosed between a chord and the corresponding arc is called the segment of a circle. The area of a segment is the area of the corresponding sector minus the area of the corresponding triangle.

Area of Segment  = Area of Sector  – Area of

The area of a sector of angle  .